Phosphoenolpyruvate carboxykinase of rat small intestine: distribution and regulation of activity and mRNA levels.

Phosphoenolpyruvate carboxykinase (PEPCK) activity is present along the length of rat small intestine and in enterocytes throughout the villus-crypt axis. There is no detectable activity in submucosal layers. Messenger RNA encoding PEPCK is detectable in rat intestinal mucosa and the relative abundance increases markedly (3- to 8-fold) during starvation or streptozotocin-diabetes. However, these changes are not matched by changes in enzyme activity which are only slightly increased (1.5-fold). The intestine of neonatal rats possesses relatively high amounts of both PEPCK activity and mRNA. Based on the distribution and regulation of intestinal PEPCK, it is proposed that the enzyme does not play a significant role in either gluconeogenesis or glutamine catabolism in adult rats.